Nr 322 scale and resolution
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NR 322: Scale and Resolution. Jim Graham & Alex Daniels Fall 2010 Chapter 2. Scale. Scale is the scale of the map relative to the true size of the items on the map e.g 1:750,000 1 unit on the map is equivalent to 750,000 units on the earth Small scale vs Large scale Which number is larger

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NR 322: Scale and Resolution

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Nr 322 scale and resolution

NR 322: Scale and Resolution

Jim Graham & Alex Daniels

Fall 2010

Chapter 2


Scale

Scale

  • Scale is the scale of the map relative to the true size of the items on the map

  • e.g 1:750,000

    • 1 unit on the map is equivalent to 750,000 units on the earth

  • Small scale vs Large scale

  • Which number is larger

    • 1 / 750,000 or 1 / 2


Map scale

Map Scale


Misunderstood terminology

Misunderstood Terminology

  • Small Scale = Large Extent

    • Think of the divisions on the scale being small

    • Miles are smaller at small scale

  • Large Scale = Small Extent

    • Think of the divisions on the scale being big

    • Miles are larger at large scale

  • Recommendation:

    • Use Large Extent or Small Extent

    • Use Low Resolution or High Resolution


Scale can vary on a map

Scale can vary on a map

  • What is the scale in kilometers on a Geographic Projection map?


Scale can vary

Scale can Vary

  • What is the scale on a google earth map?


Resolution

Resolution

  • Resolution is the ability to resolve detail

  • We mostly refer to Spatial Resolution

    • For Rasters/Grids/Digital Photos this means the size of the pixels.

    • What distance on the ground does one pixel represent?

30 Meters


30m vs 1m spatial resolution

30m vs. 1m Spatial Resolution


Washington d c 30m

Washington D.C. ~ 30m


Washington d c 5 m

Washington D.C. ~ 5 m


Resolution1

Resolution

  • High resolution is awesome, why don't we make everything 1m data or better?

  • The number of pixels increases exponentially as you increase spatial res.

Resolution x 2

Pixels x 4


High resolution big files

High Resolution ~ Big Files

  • Rasters and photos can get really big really fast.

  • Civilian satellites now can take satellite photos as high as 41 cm resolution

  • i³ in Fort Collins has 1m Satellite Photos that take 300 Gigabytes for just one area.


Low spatial resolution

Low spatial resolution

  • Low resolution averages data


Accuracy and precision

Accuracy and Precision

  • Accuracy is how close something is to the true value

  • Precision is how close of a measurement you can make

  • High accuracy doesn't mean high precision


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